Explosive composition containing ammonium nitrate and an organic sensitizer dissolved in dimethylformamide

ABSTRACT

AMMONIUM NITRATE EXPLOSIVES ARE CONVENIENTLY PREPARED BY DISSOLVING A SENSITIZING COMPOUND SUCH AS TNT IN DIMETHYL FORMAMIDE AND THEN MIXING IT AT AMBIENT TEMPERATURES WITH AMMONIUM NITRATE AND ADDITIONAL FUEL COMPONENTS. THE RESULTANT MIXTURE IS UNIFORM IN PERFORMACE OVER EXTENDED PERIODS OF TIME.

EXPLOSIVE COMPOSITION CONTAINING AMMO- NIUM NITRATE AND AN ORGANICSENSITIZER DISSOLVED IN DIMETHYLFORMAMIDE Edwin H. Nuscher and Jack D.Slater, Savannah, Ga.,

assignors to Kaiser Aluminum & Chemical Corporation, Oakland, Calif. NoDrawing. Filed Oct. 23, I968, Ser. No. 770,093

Int. Cl. C06b 9/00 US. Cl. 149-39 8 Claims ABSTRACT OF THE DISCLOSUREAmmonium nitrate explosives are conveniently prepared by dissolving asensitizing compound such as TNT in dimethyl formamide and then mixingit at ambient temperatures with ammonium nitrate and additional fuelcomponents. The resultant mixture is uniform in per formance overextended periods of time.

BACKGROUND Ammonium nitrate is a commercially desirable explosivematerial since it can be obtained relatively cheaply. However, to beeffective, the commercial crystalline or granular ammonium nitrate mustbe admixed with an oxidizable fuel material. Many organic and inorganicitems have been used as fuels. Typical organic materials are carbonblack, polysaccharides, fuel oil, tall oil, resins, and urea. Inorganicmaterials have been powdered, flaked and granular aluminum, iron,magnesium, and sulfur. Mixtures of these are frequently employed, e.g.fuel oil and aluminum.

Ammonium nitrate and oxidizable fuel mixtures are capable of exertingpowerful explosive forces. However, ammonium nitrate-fuel mixtures maybe diflicult to detonate without special boosters. For some time noworganic compounds such as mononitrotoluene, dinitrotoluene,trinitrotoluene, nitrobenzene, nitroglycerine, urea, rosin, or mixturesof these materials have been added as sensitizers or boosters.

Explosive compositions of ammonium nitrate, fuels, and sensitizers, havefound many important civil and military applications. The production ofammonium nitrate based explosives has been commercially practicalbecause of the relatively loW cost of ammonium nitrate as well as theefforts made by manufacturers to hold the use of high cost sensitizersat a minimum and to keep production techniques simple and safe.

In the preparation of ammonium nitrate based explosives sensitized withorganic compounds, an objective of the explosive art has been to securethe most practical possible intimate and uniform blend. One procedurehas been to grind ammonium nitrate and a sensitizer together in mills.Such a procedure occasionally results in a lack of uniformity in bothcomposition and properties. An other procedure has been to heat asensitizer to its melting temperatures and then mix it into ammoniumnitrate, which may also be heated. These procedures, which requiresheating or grinding of the sensitizer, presents an undesirable hazard.

DISCLOSURE It is an important object of this invention to provide asensitized ammonium nitrate composition by simply mixing a sensitizerand ammonium nitrate at ambient 3,675,235 Patented July Ill, 1972temperatures, that is temperatures between about 50 F. and about 100 F.,without heating or grinding of the composition.

Another important object of this invention is to provide an ammoniumnitrate explosive, containing a sensitizer, which is uniform inperformance over extended periods of handling, moving, or storage.

Another object of this invention is to provide an explosive mixturewhich is relatively inexpensive because ammonium nitrate is utilized asthe principal explosive material.

A further object of this invention is to provide an explosive mixturebased on ammonium nitrate and containing an additional, useful,economical and compatible fuel, in which the sensitizer is an organiccompound or mixture of organic compounds.

We have found that most organic compounds which are suitable for serviceas sensitizing materials have excellent solubility in dimethylformamide(DMF). As examples, over ambient temperatures, a solution of 55-60%dinitrotoluene (DNT), a solution of 5055% trinitrotoluene (TNT), and asolution of 5055% rosin can be prepared in DMF. At these temperatures,DMF is a liquid (melting point 61 C. and boiling point 152 C.) with avapor pressure of 3.7 mm. at 25 C. and with a reported toxicity lessthan or no greater than the sensitizing nitro compounds that might beused. DMF is also an excellent fuel in itself for the preparation of anammonium nitrate explosive composition.

We have found that the objects of this invention may be accomplished byadmixing suitable proportions of ammonium nitrate with a sensitizerwhich has been dissolved in DMF. An additional fuel component such asfuel oil, aluminum, etc., may also be incorporated. The sensitizer maybe any of the organic compounds previously recited, although anitrotoluene or rosin is preferred. A particularly useful organicmaterial is a solution of rosin in DMF because rosin may be used as boththe sensitizer and additional fuel component. Preferred compositionswill contain from about to about ammonium nitrate, about 2% to about 10%DMF, about 1% to about 6% sensitizer, and about 3% to about 10%additional fuel. The selected materials are mixed in any convenientmixing means at ambient temperature. By virtue of the nature of theingredients, the final compositions will be substantially anhydrous,i.e. less than 0.50% water, and preferably less than 0.20%. Also, thesolution of sensitizer in DMF is adsorbed into the porous ammoniumnitrate. As a result, the uniform compositions of the invention arefree-flowing, dry mixtures and they remain so over extended periods oftime.

A family of explosive mixture having a wide range of explosiveproperties can be prepared in accordance with this invention. Forexample, the finer the particle size of ammonium nitrate and/oraluminum, the greater the sensitivity of the mixture. Particularlydesirable explosive properties have been obtained with mixture in whichat least 50% of the ammonium nitrate was 20 mesh. Also, sodium nitratemay be substituted for up to 25% of the ammonium nitrate, thusincreasing the density of the overall mixture. In this way it ispossible to formulate a mixture with a density greater than 1, which isimportant if the mixture is to be detonated under water.

Mixtures prepared according to this invention were tested by detonationwith a #6 blasting cap to determine sensitivity. The power developed wasestimated by using the small lead black compression test (PhysicalTesting of Explosives U.S. Department of Commerce,

ceeding examples. They are summarized in the following table.

Percent Mix TNT DNT Inches, compres- DMF NHgNO; Fine Al Coarse A1 sion30 Mesh Control #1 #1 Control #2 lemon *Power mix #1 and #4 arecommercial ground, physical mixture containing NH4N03, TN T,'-DN '1 oil,NaNOa and aluminum powder.

Bureau of Mines, Bulletin 346, 1931). The compression of a 1 /2" x 3"lead block by a 140 gram test charge was compared with that made by a140 gram charge of flaked or granular TNT.

Examples of compositions made in accordance with this invention aredescribed below for purpose of illustration.

EXAMPLE 1 EXAMPLE 2 2.87 parts of gum rosin were dissolved in 2.78 partsof DMF at room temperature. This solution was intimately mixed into89.20 parts of NH NO which had been ground fine enough so that nodiscrete prills remained. 5.15 parts '30 mesh aluminum was evenly mixedinto the mixture.

This material was tfired in a 1 /2" diameter container on the test leadblock and gave a compression of inch. It 'was sensitive to a #6 blastingcap.

EXAMPLE 3 4.57 parts of TNT were dissolved in 5.89 parts of DMF at roomtemperature. This solution was intimately mixed into 86.27 parts of NHNO which had been ground fine enough so that no discrete prillsremained. 3.26 parts 30 mesh aluminum was distributed evenly through themixture.

The composition was fired in a 1 /2" diameter container on the test leadblock and gave a compression of inch. It was sensitive to a #6 blastingcap.

EXAMPLE 4 Additional materials, sensitive to a #6 blasting cap, wereprepared according to the procedure of the pre- What is claimed is:

1. A substantially anhydrous, uniform explosive composition comprisingammonium nitrate and a sensitizing amount of an organic sensitizerdissolved in dimethylformamide said organic sensitizer being a memberselected from the group consisting of a nitrotoluene, nitrobenzene,nitroglycerine, urea, rosin or mixtures thereof.

2. A composition of claim 1 wherein the sensitizer is a nitrotoluene.

3. A composition of claim 1 in which the sensitizer is a solution ofabout 5% to about 50% rosin in dimethylformamide.

4. A composition of claim 1 to which an additional fuel component hasbeen added.

5. A composition of claim 4 in which the additional fuel component isaluminum.

6. A composition of claim 5 wherein the sensitizer is a nitrotoluene.

7. A method for making a uniform explosive composition which comprisesmixing at ambient temperatures ammonium nitrate in a solution of anorganic sensitizer for said dimethylformamide and ammonium nitrate untila uniform mixture is obtained, said organic sensitizer being a memberselected from the group consisting of a nitrotoluene, nitrobenzene,nitroglycerine, urea, rosin or mixtures thereof.

8. The process of claim 7 wherein an additional fuel component isuniformly incorporated into the mixture.

References Cited UNITED STATES PATENTS 3,190,777 6/1965 Breza et a1.14957 3,282,752 11/1966 Clay ct a1 149-44- 3,307,986 3/1967 Grant 149443,379,587 4/1968 Cook 149-44 3,390,029 6/1968 Preckel 14944 3,406,05110/ 1968 Fearnow 14957 3,406,051 10/1968 Fearnow 149105 5 CARL D.QUARFORTH, Primary Examiner S. J. LECHERT, JR., Assistant Examiner U.S.Cl. X.R.

